1. Field of the Invention
The present invention relates to scroll compressors and more specifically to structure that helps direct and separate the flow of gas and lubricant through the compressor.
2. Description of Related Art
Scroll compressors typically comprise two facing scroll members that are contained within a compressor shell. Scroll wraps on each scroll member interleave each other to create a series of compression chambers between the wraps. Proper relative movement between the scroll members cyclically recreates compression chambers along the outer perimeter of the scroll members, where suction gas enters, and subsequently forces the chambers to spiral inward. As the chambers approach the center of the scroll members, the volume of each chamber decreases, which compresses the gas trapped within the chambers. Upon reaching the center of the scroll members, the compressed gas is discharged from the compressor shell for use.
To minimize wear, scroll compressors usually have an oil pump that draws oil from an oil sump at the bottom of the compressor shell and forces the oil to various bearings and other moving parts of the compressor. Afterwards, the oil drains back to the oil sump for reuse. The pump is usually incorporated into a rotor shaft of a motor whose primary function is to drive the movement of one or both of the scroll members.
Since the gas and oil are in open fluid communication with each other, the gas may entrain some of the oil. Then, as the compressor discharges the compressed gas, the entrained oil is discharged as well, thus reducing the level of oil in the sump. The oil may eventually return to the compressor through a suction inlet of the compressor shell; however, if the discharged gas entrains an excessive amount of oil, the compressor may be left with an insufficient amount of oil in the sump.
Various conditions can cause the gas to entrain an excessive amount of oil. More oil is entrained, for instance, when gas moves at high velocity across the surface of the oil in the sump. Also, a protruding counterweight or other irregularity at the lower end of the rotor may create a gas vortex or turbulence that can agitate the oil in the sump. High velocity gas tends to entrain oil more readily from oil surfaces that are more agitated. In some cases, the oil returning to the sump may be opposed by a strong current of gas moving in an opposite direction away from the sump. The counter flow pattern of oil and gas tends to entrain more oil. Thus, it may be beneficial to separate the gas and oil flow paths as much as possible.
Keeping the gas flow completely away from the oil sump may reduce oil entrainment but may also create an overheating problem within the motor. Since the motor's rotor shaft usually serves as the pump and as a conduit for conveying the oil from the sump to the parts needing lubrication, the motor is preferably adjacent to the sump. This usually places the oil sump and the lower end turns of the motor's stator in proximity. Directing the gas away from the sump and thus away from the lower end turns of the motor may prevent the gas from being able to cool the lower end turns. As a result, the motor may overheat.
Consequently, there is a need for a scroll compressor that provides effective gas/oil separation without sacrificing motor cooling.